While there could be other interpretations for this novel call type, it really does look like these Mexican Free-Tailed Bats are actually using "offensive" calls so that competing bats are less likely to successfully catch prey on the wing. If so, it's the first time this inter-specific jamming behavior has ever been documented.

The world of echolocation, however, is much more complicated than simply "sonar". The author of this research has also done a great deal of work studying the co-evolution of moths, some of whom have the ability to detect echolocation so they can evade an incoming bat, and some of whom have passive sonar jamming ("stealth" body parts) or even active jamming by emitting ultrasound! His website is fascinating if you're interested in learning more: Aaron Corcoran, SonarJamming.com